According to the auction house that sold it, this movie poster is from 1928. Mickey has red pants, gloves, shoes, and pupils. Which would imply that those features are out of copyright, even if they didn't appear in the cartoons until 1929 or later.
Possibly making things even more interesting, the poster *itself* doesn't appear to have a copyright notice, which as I understand it would mean that under the 1909 copyright act it was never under copyright at all in the US.
